Steam injection in gas turbines having fixed geometry components

ABSTRACT

Control means are provided for utilizing maximum tolerable amounts of steam in gas turbines having fixed geometry components under various operating conditions. Optional means include: means for automatically holding a constant cycle pressure ratio under all ambient conditions; temperature sensing control means for automatically adjusting steam injection in both low and high temperature ambients to avoid visible plumes and to avoid acid condensation, respectively; or combined temperature and humidity sensing control means for automatically optimizing steam injection under all conditions of ambient temperature and humidity.

United States Patent Kydd et al. 51 Sept. 26, 1972 [54] STEAM INJECTIONIN GAS TURBINES Primary Examiner-Carlton R. Croyle HAVING FIXED GEOMETRYAssistant Examiner-Warren Olsen COMPONENTS Attorney-Richard R. Brainard,Paul A. Frank, [72] Inventors: Paul a Kydd; William H. Day both CharlesT. Watts, Leo l. Malossl, Frank L. Neuhauser,

of Scotia, Oscar B. Waddell and Joseph B. Forman [73] Assignee: GeneralElectric Company 221 Filed: May 12, 1971 [57] ABSTRACT [21] m No;142,471 Control means are provided for utilizing maximum tolerableamounts of steam in gas turbines having fixed geometry components undervarious operating kgg g'gg conditions. Optional means include: means forauto- 'L' g matically holding a constant cycle pressure ratio under a 6all ambient conditions; temperature sensing control means forautomatically adjusting steam injection in [56] References Cited bothlow and high temperature ambients to avoid visible plumes and to avoidacid condensation, respective- UNITED STATES PATENTS ly; or combinedtemperature and humidity sensing 2,959,005 ll/l960 Zara ..60/39.55 meansautomatically Plimizing swam 3,353,360 ll/l967 Gorzegno ..150/39.3 Junder condilims of ambient temperature 2,678,531 5/1954 Miller..60/39.05 and hum'dlty- 3,649,469 3/1972 MacBeth ..6()/39.55

FOREIGN PATENTS OR APPLICATIONS 30 Claims, 7 Drawing Figures 614,10612/1948 Great Britain ..60/39.53

l ,33 ,34 32 I PRESSURE can/Mum a Wl-TiF-r' mawoucsa CIRCUIT saw? STEAMINJECTION IN GAS TURBINES HAVING FIXED GEOMETRY COMPONENTS BACKGROUND OFTHE INVENTION DESCRIPTION OF THE PREFERRED EMBODIMENT Although steaminjection, per se, of gas turbines has The injection of steam into thecombustion chamber been previously employed no consideration appears toof a gas turbine is broadly old as is shown in US. Pat. No.2,678,53l-Miller and US. Pat. No. 3,353,360- Gorzegno. The operation ofgas turbines in the steam injection mode provides greater output,because of the increased mass flow through the turbine and because ofthe higher specific heat of the turbine working fluid. A higher cycleefficiency also results, because this mass flow is obtained without theexpenditure of additional compressor power, and the steam for the steaminjection can be generated utilizing heat losses or exhaust heat whichotherwise is not effectively utilized.

SUMMARY OF THE INVENTION Control means are provided for utilizing themaximum amounts of steam that can be tolerated in the operation of gasturbines having fixed geometry components under various operatingconditions. Optional means are provided as follows: means forautomatically holding a constant cycle pressure ratio (compressordischarge pressure/ambient pressure) under all ambient conditions;temperature sensing control means for automatically adjusting steaminjection in both low and high temperature ambients to avoid visibleplumes and to avoid acid condensation, respectively; or combinedtemperature and humidity sensing control means for automaticallyoptimizing steam injection under all conditions of ambient temperatureand humidity.

BRIEF DESCRIPTION OF THE DRAWING The exact nature of this invention aswell as objects and advantages thereof will be readily apparent fromconsideration of the following specification relating to the annexeddrawing in which:

FIG. 1 is a schematic representation of one embodiment of meansaccording to this invention for automatically controlling the extent ofsteam injection employed in a fixed geometry continuous flow gasturbine;

FIG. 2 shows a second embodiment of the control voltage generator shownin FIG. 1 including ambient temperature as a control parameter;

FIG. 3 is another modification of the control voltage generator shown inFIG. 1 including both ambient temperature and ambient humidity ascontrol parameters;

FIGS. 4 and 5 considered together constitute a gas turbine performancemap setting forth output and thermal efficiency as a function of ambienttemperature at a series of turbine inlet temperatures;

FIG. 6 is a schematic representation of an automatically controlledsteam injection system according to this invention wherein in additionto the steam injection means of FIG. 1 steam is also generated from theheat in the coolant stream of a liquid cooled turbine and from the linerof the combustor and FIG. 7 is a schematic representation of a system inwhich steam is generated at a substantially fixed rate and a controlvoltage generator according to this invention is used to adjust theadmission of steam to the combustor.

have been given to the elimination of problems encountered in the use ofsteam injection. These problems include the emission of visible exhaustplumes at low ambient temperatures and the occurrence of sulfuric acidcondensation in the system under high ambient/low stack temperatureconditions. The emission of visible plumes and/or exhausts containingdroplets of acid are unacceptable in view of the increasing concern forthe quality of the environment. Further, the corrosion caused in the gasturbine exhaust system by sulfuric acid generation must be avoided.Control over the steam injection rate insuring an ecologicallyacceptable stack exhaust is highly desirable for environmental pollutionconsiderations, of course, however, it has also been found that thiscontrol capability can still further improve the operation of gasturbines using steam injection.

Investigations during the development of the instant invention haveshown that steam injection reduces the emission of nitric oxide bydiluting the combustion air and by reducing the maximum flametemperature. Reduction of flame temperature is important, because thebulk of the nitric oxide is produced at temperatures in excess of about3,400F.

In the steam injection process high-pressure steam can be used toatomize heavy fuel oil and eliminate the cost and the power consumptionof the atomizing air booster compressor. Atomization energy for improvedcombustion is virtually unlimited with the use of heat recovery steam asthe atomizing medium. Additional advantages also accrue in that by usinghigh-pressure steam as the atomizing medium the problem of forma tion ofdeposits in the turbine and in the heat recovery boiler is reduced.Further, by concentrating the steam flow in the primary zone of thecombustor the nitric oxide emission can be even more effectivelyreduced.

It has also been shown during the aforementioned investigations thateven though visible plume-free operation of gas turbines should bepossible at ambient temperatures above about F when using verysubstantial steam flows, the problem of the condensation of sulfuricacid in the stack (whereupon this objectionable corrosive condensate ispresent in the stack exhaust) still remains. Further, the generation ofvisible plumes at ambient temperatures below 75F is still a problem.Both of these troublesome conditions can be eliminated by the practiceof at least one of the several options presented in the instantinvention.

FIG. 1 schematically represents a gas turbine 10 having fixed geometrycomponents; compressor 11, combustor l2 and turbine 13. Gas turbine 10has been provided with steam injection means and controls therefor inaccordance with the instant invention.

The steam injection means comprises a steam separator 14 [which may forexample be of the drum variety], conduit 16 carrying a hot water/steammixture to steam separator 14, conduit 17, which conducts steam fromsteam separator 14 to the combustor 12, conduit 18 which removes liquidwater to the feedwater pump 19, conduit 20 which conducts water toboiler 21, inlet water conduit 22 for water makeup and valved blowldownline 23. A flash tank and pressure reducing valve combination as isshown in the aforementioned Gorzegno patent (incorporated by reference)may be substituted for steam separator 14.

During operation in the steam injection mode compressor 11 takes inatmospheric air and forces it under substantial superatmosphericpressure into combustor 12. Fuel is supplied to combustor 12 throughfuel inlet 24 and steam is injected into combustor 12 via line 17.Either high-pressure air or the steam (or suitable mixtures thereof) maybe employed to atomize the fuel in combustor 12. Combustion of the fuelin combustor 12 produces hot gases, which pass through turbine 13, whereexpansion of the hot gases occurs with the generation of mechanicalenergy part of which drives compressor 12 via shaft 26 and part of whichis available to drive a load via shaft 27.

Control voltage generator 31 consists of the preset voltage source 32,pressure transducer 33 and comparator circuit 34. These components areelectrically connected as shown. When operating, voltage source 32continuously applies a fixed biasing voltage E to comparator circuit 34and pressure transducer 33 continuously applies voltage E, to comparatorcircuit 34, E being a voltage that is proportional to the compressordischarge pressure applied to pressure transducer 33 via conduit 36.Comparator circuit 34 is adjusted so that for a voltage Ep reflecting acompressor discharge pressure equal to the selected operating value ofcycle pressure ratio selected as described hereinabove, the bias voltageE is just compensated.

In the event of a change in the compressor discharge pressure, voltage Ewill not be equal to bias voltage E and the voltage error is the controlvoltage (E,;) that is thereby generated (and amplified, if required) issupplied to by-pass unit 37 (with motorized actuator 37a), e.g., adamper actuator (as manufactured by the General Electric Company,Instrument Department, Lynn, Mass), so as to change the position ofbaffle 37b and thereby modify the amount of exhaust gas passing throughboiler 21 to reduce and then eliminate the error. Thus, if voltage E, istemporarily greater than bias voltage E a negative control voltage E; isgenerated resetting bypass actuator 37a to decrease the amount ofexhaust gas from turbine 13 passing through line 38, bypass unit 37,line 38a and boiler 21. This change results in a decrease in the amountof steam generated in boiler 21 and separated in steam separator 14thereby decreasing the steam input to combustor 12. If the reversesituation occurs (E, is less than E a positive control voltage E resultsand bypass actuator 37a is readjusted so as to increase the exhaust flowthrough boiler 21 and decrease the amount of exhaust passing through theexhaust conduit 39 and mixer 40 to the stack. The changes in steam flowso accomplished will reduce and eliminate control voltage E changing thepressure ratio across compressor 12 by changing the amount of mass flowoccurring at fixed temperature through the fixed geometry turbine. Ifdesired, some of the injected steam is introduced into the head end ofthe combustor and the balance of the input is introduced thereindownstream of the head.

Valve in steam line 17 is controlled in the conventional manner (as bysensing the rotational speed of shaft 27) to compensate for largeincreases or decreases in gas turbine load. Valve 25 may be athrottling/shut-off type valve or a bypass valve.

There are at least two types of situations in which the automaticelimination of visible exhaust plume and exhaust system corrosion mustbe accomplished at some turbine inlet temperature lower than thetemperature at which steam injection which maintains constant pressureratio will do so automatically. In such situations the control voltagegenerator device 31 will not provide sufficiently sophisticated control.Either of the control voltage generators shown in FIGS. 2 and 3 may thenbe employed to effect control such that the maximum amount of steam isgenerated (and injected) as required for maximum output and thermalefficiency over the preselected range of ambient temperatures. Examplesof the aforementioned types of situations are as follows:

a. when it is desired to operate the machine at a turbine inlettemperature below the maximum turbine inlet temperature thereof(although such operation is within its capability) in order to achievereduced power output but yet operate in this regime at maximum steamflow and efficiency and b. when the compressor/turbine combination issuch that the turbine cannot tolerate as high an inlet temperature as isnecessary for the maintenance by steam injection of the maximum pressureratio over the full preselected range of ambient temperatures.

The device of FIG. 2 supplies a voltage to automatically control steamgeneration as a function of ambient temperature while the device shownin FIG. 3 supplies a voltage to automatically control steam generationas a function of both the ambient temperature and ambient relativehumidity (RH). All components shown in connection with all the controlmeans disclosed herein are commercially available items.

The device 41 shown in FIG. 2 is interchangeable with control voltagegenerator 31 shown in FIG. 1. Pressure transducer 42 is hydraulicallyconnected via line 36 to the compressor discharge. Voltage E having avalue proportional to the compressor discharge pressure is supplied tocomparator circuit 43 as described hereinabove. Temperature sensor 44(e.g., a thermocouple or temperature transmitter such as GE/M AC type550 manufactured by the General Electric Company, Instrument Department,Lynn, Mass.) is located at or near the compressor inlet emitting avoltage E reflecting the ambient temperature conditions. Temperaturesensor 44 is electrically connected to function generator 46 (e.g.,GE/MAC type 566 function generator manufactured by the General ElectricCompany, Instrument Department, Lynn, Mass.) as shown so as to applyvoltage E thereto. In function generator 46 (set for a I00 percentrelative humidity condition), a bias voltage E is generated as afunction of voltage E and, as a result, reflects the effect of anyambient temperature in the preselected range at I00 percent RH. VoltagesE and Ep are applied to comparator circuit 43 in the manner describedhereinabove for comparator circuit 34. The value of the voltage error(control voltage E if any, determines the setting of motorized bypassunit 37 in the same manner as described hereinabove.

Thus, should the ambient temperature decrease below the point at which aconstant pressure ratio can be maintained by steam injection withoutvisible plume, there will be automatic compensation of the rate of steaminjection, because the electrical control signal B; will automaticallyrelate to the selected compressor discharge pressure compensated for lowambients. Thus, control voltage E (via bypass actuator 370) will adjustthe rate of steam injection to com-' bustor 12 as required to avoidvisible plumes in the exhaust. Similarly, should the ambient temperatureincrease above the point at which a constant pressure ratio can bemaintained by steam injection without forming acid condensate in theexhaust, control voltage E; will automatically properly adjust the rateof steam injection to combustor 12 to eliminate the acid condition. Thismode of operation will allow satisfactory performance at all ambientrelative humidities, but must sacrifice the opportunity to add moresteam at ambient humidities lower than I00 percent RH.

The control voltage generator 51 includes pressure transducer 52, theelectrical output (voltage Ep) of which passes to comparator circuit 53as described hereinabove and the electrical signal E, is comparedtherein to biasing signal E which latter voltage factors into theautomatic control function the parameters of ambient temperature andambient humidity. Both a temperature sensor and a humidity sensor (e.g.,of the surface ion exchange type as manufactured by the Amlab Company ofEssex, Conn., used in a bridge circuit with thermistor compensation fortemperature effects) are located at or near the compressor inlet andthese sensors respectively emit electrical signals E and E The humiditysensor 54 is adjusted so that at 100 percent RH the output voltage E iszero and at zero relative humidity E is one unit. Temperature sensor 55is electrically connected to each of function generators 56 and 57.Function generator 56 emits voltage E as some function of E (andtherefore as a function of the ambient temperature) at 100 percent RH.Function generator 56 is electrically connected to summing junction58,which in turn is electrically connected to comparator circuit 53.

The electrical signal E impressed on function generator 57 generates thevoltage designated as AE This electrical signal (voltage AE reflects anyrequisite correction voltage for the actual ambient temperature at arelative humidity of zero or, in effect is indicative of the rate ofsteam injection that should be employed under these conditions. VoltageA5,, is then further modified (as described hereinbelow) ininterpolation circuit 59 (e.g., voltage multiplier, type 5648manufactured by General Electric Company, instrument Department, Lynn,Mass.) to reflect the actual ambient humidity sensed by humidity sensor54. Voltage E emitted by humidity sensor 54 reflects the actual ambienthumidity and is indicative of the fraction of voltage AE that can formpart of the bias voltage to be applied to comparator circuit 53.

As shown, both voltage E and voltage AE are introduced to interpolationcircuit 59. The interpolation circuit 59 electrically multiplies voltageAE by voltage E and the product thereof (voltage AE reflects theincremental rate of steam injection that can be tolerated at the ambienttemperature and ambient relative humidity over the rate of steaminjection permissible for the ambient temperature/100 percent RHcondition. Interpolation circuit 59 is electrically connected to summingjunction 58 to which the electrical signals E (representing rate ofsteam injection for the ambient temperature at percent RH) and M5(representing the increment of added rate of steam injection for ambienthumidity) are introduced. ln summing junction 58, E and A5 are added toproduce the net biasing voltage E impressed upon comparator circuit 53.Any resulting error signal E; from comparator circuit 53 controls thesetting of actuator 37a in the same manner described hereinabove therebyproviding automatically optimized operation at all ambient temperatures(in the preselected range) and all ambient relative humidities.

Although the control devices illustrated herein are electrical innature, this invention is intended to encompass hydraulic, pneumatic andmechanical analogs of these electrical devices. In each instance, it isrequired to produce a signal quantitatively related to the pressureratio and interrelate a bias signal therewith. The bias signal may havea constant value or may be variable either as a function of ambienttemperature or as a function of both ambient temperature and ambienthumidity.

Any one of the three optional control voltage generators describedhereinabove may be utilized for controlling the steam injection into anygiven gas turbine. The choice of which one is to be used will bedetermined by the characteristics of the gas turbine in question, therange of ambient temperature and rela' tive humidity over which themachine must operate and whether the power output and efficiency are tobe optimized with regard to relative humidity.

The characteristics of the gas turbine which are important are thecompressor map (pressure ratio versus air flow at various speeds), whichdefines the stall or pulsation limit as a function of speed, and thefirst stage turbine nozzle area. The turbine nozzle area must be largeenough that the compressor does not stall at maximum turbine inlettemperature and minimum ambient air temperature under which conditionsthe air flow and pressure ratio of the compressor are high due to thehigh inlet air density. Consequently at higher ambient temperaturesadditional mass flow can be accepted by the turbine without stalling thecompressor.

The first step in selecting a control voltage generator from the optionsdisclosed herein for a given gas turbine is to choose a turbine inlettemperature and steam flow which provides the desired balance betweenpower output and efiiciency at the design point. High turbine inlettemperatures provide maximum output (HQ 4). Lower turbine inlettemperatures and higher steam flow produce a higher thermal efficiency(FIG. 5) down to the point at which the exhaust temperature is too lowto generate the required amount of steam or at which the decline inavailable energy due to reduced turbine inlet temperature is no longeroffset by the increase in available energy from the permissible increase in steam addition. The above-noted combination of turbine inlettemperature and steam flow will be chosen to increase the pressure ratioto the maximum that the compressor can deliver with an adequate stallmargin.

The next step in selecting the control system is to investigate theperformance of the gas turbine over the intended range of ambienttemperature. The objective is to maintain optimum performance over aswide a range of ambient conditions as are to be encountered. This ismost easily accomplished by holding turbine inlet temperature constantvia the conventional exhaust temperature measurement and fuel controlsystem and holding pressure ratio constant at its maximum value bycontrolling the rate of steam injection. It may be that for the givengas turbine components and turbine inlet temperature constant pressureratio operation can be achieved over the entire range of expectedambient temperature. In this case control voltage generator 31 willsuffice.

If at low ambient temperatures and 100 percent RH it is found eitherthat the exhaust moisture content is such that a visible plume forms, orthat at high ambient temperatures and 100 percent RH,acid condensationoccurs due to excessive steam flow and correspondingly low stacktemperature, it will be necessary to restrict the steam flow into thecombustor at low temperatures, at high temperatures or both. Thisrestriction of steam flow, which will reduce the pressure ratio and theperformance of the gas turbine at extreme ambient conditions can beaccomplished with control voltage generator 41.

If it is desired to take advantage of the fact that low ambient relativehumidity will reduce the tendency to generate an exhaust plume or stackcondensation, one can extend the region of maximum steam flow andperformance under low relative humidity conditions by using controlvoltage generator 51.

In all cases it is desired to achieve the maximum steam flow permittedby the boundaries imposed by exhaust plume formation, compressor stall,and acid condensation, at the chosen turbine inlet temperature. Higherturbine inlet temperatures widen the range of ambient temperature overwhich operation at constant maximum pressure ratio is possible. Theoperating boundaries for a representative gas turbine at differentturbine inlet temperatures are shown in H65. 4 and 5. Thus, foroperation at each of the turbine inlet temperatures shown, thecompressor stall boundary lies between letters a and b; the exhaustplume boundary lies to the low ambient temperature side of letter a andthe acid condensation boundary lies to the high am bient temperatureside of letter b. For operation between letters a and b the pressureratio is constant. This map further illustrates the substantial changein thermal efficiency and output between operation in the steaminjection mode and operation without steam injection.

The generation of the data required to prepare a turbine performance mapsuch as FIGS. 4 and 5 (considered together) requires a considerableamount of cut-and-try calculating and is, therefore, most effectivelyaccomplished by the use of a computer, e.g., time-sharing. Thedevelopment of a suitable computer program would employ steps asfollows:

a. tentative selection of a range of turbine inlet temperaturesproviding a desired balance between thermal efficiency and power outputfor the gas turbine,

b. selection from the compressor map of a range of operating pressureratios for the gas turbine along the I00 percent speed curve; thehighest pressure ratio being that pressure ratio which the compressorcan deliver without stalling and the lowest pressure ratio being thepressure ratio for the non-steam injected condition at lowest ambienttemperature,

c. selection of an operating range of ambient temperatures,

d. calculation of the range of operating turbine inlet temperatures tobe employed using known relationships of gas properties (at differenttemperatures and steam content) and turbine efficiency (as a function ofpressure ratio, turbine inlet temperature, steam content and fuelcontent),

c. selection of a range for the amount of steam to be injected (i.e.,rates of steam injection) into the gas,

f. calculation of a map of the efficiency of the turbine alone as afunction of the parameters in the three selected ranges (pressure ratio,turbine inlet temperature and steam injection),

g. selection of some value of turbine inlet temperature from thecalculated temperature range,

h. selection of an ambient temperature and a relative humidity of eitherzero or percent,

i. calculation of the compressor efficiency for the selected ambientconditions to determine the maximum pressure ratio available from thecompressor,

j. calculation of the amount of steam and fuel flow required to createthis maximum pressure ratio at the selected turbine inlet temperature,

It. determination of the efficiency of the turbine itself from theturbine performance map for the selected turbine inlet temperature,maximum pressure ratio and gas properties,

1. calculation of the turbine exhaust temperature (accounting for theeffects of cooling and diluting of the gas flow),

m. calculation of the stack temperature considering any heat removalfrom the exhaust gas and, knowing the stack temperature, determiningwhether stack corrosion (acid condensation) will occur, and

n. determination of whether visible plume will be generated under theselected operating conditions at the selected ambient temperature andrelative humidity by calculating the relative humidity of successivedilutions of stack effluent with the ambient air.

If it be determined that either an acid condition or visible plume wouldoccur, the amount of steam being injected is too great. In such case,the procedure will have to be repeated using a smaller steam flow andconsidering the changes (lower pressure ratio) that accompany thereduced steam injection.

If neither acid condensation nor visible plume occur, the aforementionedsteps are repeated using a different set of ambient conditions. When asufficiently large number of sets of ambient conditions have beenconsidered (e.g., at temperature increments of about 20F) one curve ofgas turbine thermal efficiency and output will be generated for thesingle selected turbine inlet temperature as described hereinabove.Thereafter, the procedure is repeated until a map of gas turbine thermalefficiency and output referred to hereinabove (FIGS. 4 and 5 has beenprepared for different turbine inlet temperatures (at increments ofabout 100F). This map provides the option of selecting at will a turbineinlet temperature for optimizing the combination of gas turbine thermalefficiency and gas turbine output (consistent with machinecapabilities). Having determined this map, the method describedhereinabove for the determination of the several options may be carriedout.

If the gas turbine is one that may be operated at less than 100 percentspeed a tachometer with a signal output proportional to speed may beintroduced to sense the compressor speed and adjust the sensing of thepressure ratio (described hereinbelow) to reflect changes in speed. Withknown gas turbine construction, the selected ambient temperature rangemay be as narrow as about 60F or as wide as at least llF depending uponthe selected turbine inlet temperature. The higher the turbine inlettemperature, the greater the available ambient temperature range. By wayof example, in a General Electric M87000 gas turbine at peak reserveturbine inlet temperature the operating ambient temperature rangeavailable, which is free of visible plume or acid condensation in theexhaust, is 1 F (from 0 to 1 10F) at 14.17 psia inlet.

The unexpected aspect of this invention is that having made theaforementioned determinations, the rate (e.g., pounds of steam/hour) ofinjection of steam remains the only control parameter that is requiredto simultaneously achieve:

a. the maximum power and efficiency of which the machine is capable inthe selected operating range of ambient temperature,

b. freedom from visible plume and c. freedom from the formation of acidcondensation.

This invention, thus, provides optional means that enable control of thesteam injection rate. These devices vary in their capabilities foraccommodating the extent of ambient temperature range, when the pressureratio is not held constant. In the simplest arrangement (control signalgenerator device 31) the selected pressure ratio must be held constantand the turbine is operated at the constant selected turbine inlettemperature.

Increased efficiency can be obtained by utilizing superheated steam witha penalty of a slightly higher rate of production of nitric oxide. Stillfurther increases in specific output and efficiency can be achieved byincreasing the turbine inlet temperature. This is made possible byutilizing internal cooling. Arrangements for liquid cooling aredescribed in U.S. Pat. Nos. 3,446,48 l Kydd and 3,446,482l(ydd. Internalcooling, of course, results in heat losses from the gas stream. However,by using this lost heat to generate steam for injection into the gasturbine in addition to that generated from the turbine exhaust,approximately 70 percent of the performance decrease due to the heatlosses can be recovered.

The liquid-cooled turbine parts actually function as a boiler in thecooling sequence. The liquid coolant may either be circulated in a fullyclosed circuit or, in the case of water as the coolant, in an opencircuit from which the steam that is generated may be withdrawn andreplaced with make-up water. The former arrangement has the advantage ofminimizing contaminant content. Such is the arrangement shown in FIG. 6.

Gas turbine 60 comprises compressor 61, combustor 62 and liquid-cooledturbine 63. In addition to the steam injection means and control meanstherefor shown in FIGS. 1-3 the liquid coolant for turbine 63 and liquidcoolant for com bustor 62 are used as sources of steam generation. Therate of steam generation from these added sources is fixed by the amountof cooling required and is substantially constant. Although the rate ofsteam generation (and steam injection) is not subject to the controlmeans for the exhaust-generated steam, this does not pose a problem,because the turbine inlet temperature for a liquid-cooled turbine may beset sufficiently high to adequately accommodate the maximum rate ofsteam generation from the liquid coolant for turbine 63 and from thecooling of the liner of combustor 62 without visible plume or acidcondensate formation.

As in the arrangement shown in FIG. 1, the flow bypass 64 receivesexhaust gas from turbine 63 via line 66. Motorized actuator 64a receivescontrol voltage E; from control voltage generator 67 electricallyconnected thereto and fixes the position of damper 64b in response tovoltage 5;. The position of damper 64b determines what proportion of theexhaust gas passes through bypass unit 64 to boiler 68 via line 66a andwhat proportion of the exhaust gas passes through bypass unit 64 tomixer 69 via line 71. Control voltage generator 67 may be any of theoptions 31, 41 or 51 described hereinabove.

Thus, water circulated by pump 72 through line 73 passes throughcombustor liner 74, heat exchanger 76 and boiler 68. Steam generationmay occur in heat exchanger 76 and liner 74 and will always occur inboiler 68 depending on the setting of damper 64b. The steam/watermixture proceeds to steam separator 77 wherein liquid and steam areseparated, the liquid passing via line 78 to feed pump 72. Valvedblow-down line 79 connected to conduit 78 is used to removecontaminating material.

Steam from steam separator 77 passes to combustor 62 via line 81. Valve82 in steam line 81 is controlled in the conventional manner tocompensate for large increases or decreases in gas turbine load. Fuel issupplied to combustor 62 via pipe 83 and compressed air flows tocombustor 62 from compressor 61 to burn the fuel and generate hot gases,which pass to liquid-cooled turbine 63.

In alternate construction (not shown) instead of employing a fullyclosed circuit for the turbine liquid coolant and passing the water flowin line 73 through heat exchanger 74, the turbine cooling circuit wouldbe made part of the steam injection circuit.

If desired, the exhaust of the turbine may be used in part or in wholeto generate steam at a substantially constant rate in which case theadjusting means would be disposed between the steam generating means andthe combustor with which it is in flow communication. The controlvoltage generator options of this invention would then be used tocontrol the admission of steam to the combustor, the steam not injectedinto combustor 62 being diverted to other uses, such as process steam orspace heating. Such an arrangement is shown in FIG. 7 in which elementsthe same as those in FIG. 1 have like numerals. Flow splitter 91 with anadjustable baffle is connected between exhaust lines 38 and 38a. Thebaffle is positioned so that the amount of exhaust gas passing throughboiler 21 is sufficient to generate steam at the maximum useable rate.Control voltage generator 92 would be a modified version of options 31,41, 51 described hereinabove and controls the admission of steam tocombustor 12 by adjusting the setting of bypass unit 93 in which baffle93b is positioned by motor actuator 93a. Unused steam is conducted to analternate use via pipe 94. if too much steam is being generated for thecombined demands of steam injection and the alternate use, the baffle inflow splitter 91 is reset.

The proper setting of flow splitter 91 will, therefore, depend on therequirements for injection steam and for the alternate use and theamount of steam generated in excess of that required for steam injectionwill affect the stack gas temperature. If the stack gas temperature isreduced to too low a level, the amount of steam that may be injected atlow and at high ambient temperatures without the formation of visibleplume or acid .condensate will be reduced. A control signal derived fromstack gas temperature sensor 96 should, therefore, be used to generatean additional signal to control voltage generator 92 contributing tobias voltage E in the same manner as humidity sensor 54 andinterpolation circuit 59 contribute to signal E in control voltagegenerator 51.

As an alternate to this modification, the stack gas temperature can beraised and additional steam can be generated by the use of asupplemental burner (not shown), that would be located between flowsplitter 91 and boiler 21.

Conditions may be encountered in which it is preferred to use a sourceof steam, which employs some heat energy source for the conversion ofwater to steam other than the turbine exhaust or coolant streams. insuch instances the source of steam may be placed in flow communicationwith the combustor with a control voltage generator of this inventionbeing used either to adjust the rate at which heat energy is providedfor the steam generating function (as in FIGS. 1 and 6) or to adjust theadmission of steam to the combustor (as in FIG. 7).

By utilizing the arrangements of the instant invention for automaticallycontrolling steam injection, very significant improvements inperformance resulting from optimized steam injection may be achieved invarying degrees in conventional gas turbines having fixed geometrycomponents depending upon which option is selected.

The control devices of this invention may be incorporated either intoexisting machines or into new machines as described herein.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. In a gas turbine power plant wherein the turbine is mechanicallyconnected to and drives a compressor; said compressor suppliescompressed air to a combustor in flow communication therewith; steaminjecting means including steam generating means is in flowcommunication with said combustor and generates and supplies steamthereto; means in flow communication with said combustor supplies fuelthereto for combustion thereof with air in said combustor for thegeneration of hot gases. and said combustor supplies the hot gasesgenerated therein to said turbine being in flow communication therewith,the combination with said steam generating means of means toautomatically control the generation of steam for admission to saidcombustor, said control means comprising:

a. means in flow communication with said compressor for generating acontrol signal and b. means connected to said control signal generatingmeans and responsive to said control signal for adjusting the rate ofheat energy input to said steam generating means.

2. The combination of claim 1 wherein said steam generating means is inflow communication with the exhaust system of said turbine and saidadjusting means determines the flow of exhaust gas thereto.

3. The combination of claim I wherein said steam generating meanscomprises a first steam generator in flow communication with the exhaustsystem of said turbine and a second steam generator in series with saidfirst steam generator, said first steam generator alone having theexhaust gas input thereto adjustable by said adjusting means.

4. The combination of claim 1 wherein the means for generating a controlsignal comprises:

a. electrical signal comparing means having first and second inputs andhaving an output, said output being electrically connected to saidadjusting means,

. means electrically connected to said first input of said comparingmeans and in flow communication with the compressor discharge forsensing the compressor discharge pressure and generating apressure-response signal quantitatively related thereto and c. meanselectrically connected to said second input of said comparing means forapplying a bias signal thereto, said comparing means supplying a controlsignal to said adjusting means via said output when the relationshipbetween said bias signal and said pressure-response signal deviates fromsome predetermined value.

5. The combination of claim 4 wherein said means for applying a biassignal is a fixed voltage source.

6. The combination of claim 4 wherein said means for applying a biassignal includes a voltage generator and a temperature sensor having anelectrical signal output quantitatively related to the temperaturesensed, said temperature sensor being located adjacent the inlet to saidcompressor and being electrically connected to said voltage generator,said voltage generator being electrically connected to said second inputand the bias signal generated thereby being quantitatively related tothe signal from said temperature sensor.

7. The combination of claim 4 wherein the means for applying a biassignal includes a temperature sensor having an electrical signal outputquantitatively related to the temperature sensed; first and secondvoltage generators electrically connected at their respective inputs tosaid temperature sensor; a humidity sensor hav ing an electrical signaloutput quantitatively related to the relative humidity sensed; a voltagemultiplier having separate inputs electrically connected to the outputsof said second voltage generator and said humidity sensor, respectively;and the outputs of said first voltage generator and said voltagemultiplier being electrically connected to a summing junction, the biassignal output of said summing junction being electrically connected tosaid comparing means and said temperature sensor and said humiditysensor being located adjacent the inlet to said compressor.

8. The combination of claim 4 wherein the means for sensing andgenerating a pressure-response signal is a pressure transducer.

9. The combination of claim 1 wherein said adjusting means is a flowbypass having powered actuating means, said flow bypass being in flowcommunication with said steam generating means.

10. The combination of claim 2 wherein said adjusting means is a flowbypass having powered actuating means, said flow bypass being in flowcommunication with the outlet of said turbine, with said steamgenerating means and with mixing means located downstream in the turbineexhaust system.

11. In a gas turbine power plant wherein the turbine is mechanicallyconnected to and drives a compressor; said compressor suppliescompressed air to a combustor in flow communication therewith; steaminjecting means including steam generating means is in flowcommunication with said combustor and generates and supplies steamthereto; means in flow communication with said combustor supplies fuelthereto for combustion thereof with air in said combustor for thegeneration of hot gases, and said combustor supplies the hot gasesgenerated therein to said turbine being in flow communication therewith,the combination with said steam generating means of means toautomatically control steam flow to said combustor, said control meanscomprising:

a. means in flow communication with said compressor for generating acontrol signal and b. means for adjusting the admission of steam to saidcombustor, said adjusting means being in flow communication with bothsaid steam injecting means and said combustor and being automaticallyresponsive to said control signal.

12. The combination of claim 11 wherein said steam generating means isin flow communication with the exhaust system of said turbine.

13. The combination of claim 11 wherein the means for generating acontrol signal comprises:

a. electrical signal comparing means having first and second inputs andhaving an output, said output being electrically connected to saidadjusting means,

b. means electrically connected to said first input of said comparingmeans and in flow communication with the compressor discharge forsensing the compressor discharge pressure and generating apressure-response signal quantitatively related thereto and c. meanselectrically connected to said second input of said comparing means forapplying a bias signal thereto, said comparing means supplying a controlsignal to said adjusting means via said output when the relationshipbetween said bias signal and said pressure-response signal deviates fromsome predetermined value.

14. The combination of claim 13 wherein said means for applying a biassignal is a fixed voltage source.

15. The combination of claim 13 wherein said means for applying acontrol bias signal includes a voltage generator and a temperaturesensor having an electrical signal output quantitatively related to thetemperature sensed, said temperature sensor being located adjacent theinlet to said compressor and being electrically connected to saidvoltage generator, said voltage generator being electrically connectedto said second input and the bias signal generated thereby beingquantitatively related to the signal from said temperature sensor.

16. The combination of claim 13 wherein the means for applying a biassignal includes a temperature sensor having an electrical signal outputquantitatively related to the temperature sensed; first and secondvoltage generators electrically connected at their respective inputs tosaid temperature sensor; a humidity sensor having an electrical signaloutput quantitatively related to the relative humidity sensed, a voltagemultiplier hav ing separate inputs electrically connected to the outputsof said second voltage generator and said humidity sensor, respectively;and the outputs of said first voltage generator and said voltagemultiplier being electrically connected to a summing junction, theoutput of said summing junction being electrically connected to saidcomparing means and said temperature sensor and said humidity sensorbeing located adjacent the inlet to said compressor.

17. The combination of claim 13 wherein the means for sensing andgenerating a pressure-response signal is a pressure transducer.

18. The combination of claim 11 wherein said adjusting means is a flowby-pass having powered actuating means.

19. In a gas turbine power plant wherein a liquidcooled turbine ismechanically connected to and drives a compressor; said compressorsupplies compressed air to a combustor in flow communication therewith;steam injecting means including steam generating means is in flowcommunication with said combustor and supplies steam thereto; means inflow communication with said combustor supplies fuel thereto forcombustion thereof with air in said combustor for the generation of hotgases and said combustor supplies the hot gases generated therein tosaid turbine being in flow communication therewith, the combination withsaid steam injecting means of:

a. first steam generating means in flow communication with the exhaustsystem of said turbine,

b. second steam generating means in series with said first steamgenerating means; said second steam generating means being in heatexchange relationship with the cooling circuit of said turbine,

c. means in flow communication with said compressor for generating acontrol signal and d. means connected to said control signal generatingmeans and responsive to said control signal for ad justing the flow ofexhaust gas to said first steam generating means.

20. The combination of claim 19 wherein the means for generating acontrol signal comprises:

a. electrical signal comparing means having first and second inputs andhaving an output, said output being electrically connected to saidadjusting means,

b. means electrically connected to said first input of said comparingmeans and in flow communication with the compressor discharge forsensing the compressor discharge pressure and generating apressure-response signal quantitatively related thereto and c. meanselectrically connected to said second input of said comparing means forapplying a bias signal thereto, said comparing means supplying a controlsignal to said adjusting means via said output when the relationshipbetween said bias signal and said pressure-response signal deviates fromsome predetermined value.

21. The combination of claim wherein said means for applying a biassignal is a fixed voltage source.

22. The combination of claim 20 wherein said means for applying a biassignal includes a voltage generator and a temperature sensor having anelectrical signal output quantitatively related to the temperaturesensed, said temperature sensor being located adjacent the inlet to saidcompressor and being electrically connected to said voltage generator,said voltage generator being electrically connected to said second inputand the bias signal generated thereby being quantitatively related tothe signal from said temperature sensor.

23. The combination of claim 20 wherein the means for applying a biassignal includes a temperature sensor having an electrical signal outputquantitatively related to the temperature sensed; first and secondvoltage generators electrically connected at their respective inputs tosaid temperature sensor; a humidity sensor hav ing an electrical signaloutput quantitatively related to the relative humidity sensed; a voltagemultiplier having separate inputs electrically connected to the outputsof said second voltage generator and said humidity sensor, respectively;and the outputs of said first voltage generator and said voltagemultiplier being electrically connected to a summing junction, the biassignal output of said summing junction being electrically connected tosaid comparing means and said temperature sensor and said humiditysensor being located adjacent the inlet to said compressor.

24. The combination of claim 20 wherein the means for sensing andgenerating a pressure-response signal is a pressure transducer.

25. The combination of claim 19 wherein said adjusting means is a flowbypass having powered actuating means, said flow bypass being in flowcommunication with said steam generating means.

26. The combination of claim 19 wherein said adjusting means is a flowbypass having powered actuating means, said flow bypass being in flowcommunication with the outlet of said turbine, with said steamgenerating means and with mixing means located downstream in the turbineexhaust system.

27. In the operation of a gas turbine power plant in the steam injectionmode wherein the following steps are performed: generating steam fromliquid water; compressing atmospheric air to superatmospheric pressure;passing the compressed air to a combustion zone, where fuel isintroduced and continuous combustion occurs; passing the generated steamto said combustion zone, and passing hot gases continuously from saidcombustion zone through an expansion zone where mechanical energy isabstracted in substantially greater amount than the mechanical energyabsorbed in the compression step, the combination with said series ofstep of:

a. automatically controlling the flow of steam to said combustion zoneby means of a control signal, said gontrol si nal esulting from theinterrelation of a ias signa an a signa quantitative y comparable to thecompressor pressure ratio.

28. The steps of operation of a gas turbine power plant as recited inclaim 27 wherein the bias signal is a constant voltage signal.

29. The steps of operation of a gas turbine power plant as recited inclaim 27 wherein the bias signal is quantitatively related to theambient temperature.

30. The steps of operation of a gas turbine power plant as recited inclaim 27 wherein the bias signal is quantitatively related both to theambient temperature and to the ambient humidity.

* k I! i t

1. In a gas turbine power plant wherein the turbine is mechanicallyconnected to and drives a compressor; said compressor suppliescompressed air to a combustor in flow communication therewith; steaminjecting means including steam generating means is in flowcommunication with said combustor and generates and supplies steamthereto; means in flow communication with said combustor supplies fuelthereto for combustion thereof with air in said combustor for thegeneration of hot gases, and said combustor supplies the hot gasesgenerated therein to said turbine being in flow communication therewith,the combination with said steam generating means of means toautomatically control the generation of steam for admission to saidcombustor, said control means comprising: a. means in flow communicationwith said compressor for generating a control signal and b. meansconnected to said control signal generating means and responsive to saidcontrol signal for adjusting the rate of heat energy input to said steamgenerating means.
 2. The combination of claim 1 wherein said steamgenerating means is in flow communication with the exhaust system ofsaid turbine and said adjusting means determines the flow of exhaust gasthereto.
 3. The combination of claim 1 wherein said steam generatingmeans comprises a first steam generator in flow communication with theexhaust system of said turbine and a second steam generator in serieswith said first steam generator, said first steam generator alone havingthe exhaust gas input thereto adjustable by said adjusting means.
 4. Thecombination of claim 1 wherein the means for generating a control signalcomprises: a. electrical signal comparing means having first and secondinputs and having an output, said output being electrically connected tosaid adjusting means, b. means electrically connected to said firstinput of said comparing means and in flow communication with thecompressor discharge for sensing the compressor discharge pressure andgenerating a pressure-response signal quantitatively related thereto andc. means electrically connected to said second input of said comparingmeans for applying a bias signal thereto, said comparing meanS supplyinga control signal to said adjusting means via said output when therelationship between said bias signal and said pressure-response signaldeviates from some predetermined value.
 5. The combination of claim 4wherein said means for applying a bias signal is a fixed voltage source.6. The combination of claim 4 wherein said means for applying a biassignal includes a voltage generator and a temperature sensor having anelectrical signal output quantitatively related to the temperaturesensed, said temperature sensor being located adjacent the inlet to saidcompressor and being electrically connected to said voltage generator,said voltage generator being electrically connected to said second inputand the bias signal generated thereby being quantitatively related tothe signal from said temperature sensor.
 7. The combination of claim 4wherein the means for applying a bias signal includes a temperaturesensor having an electrical signal output quantitatively related to thetemperature sensed; first and second voltage generators electricallyconnected at their respective inputs to said temperature sensor; ahumidity sensor having an electrical signal output quantitativelyrelated to the relative humidity sensed; a voltage multiplier havingseparate inputs electrically connected to the outputs of said secondvoltage generator and said humidity sensor, respectively; and theoutputs of said first voltage generator and said voltage multiplierbeing electrically connected to a summing junction, the bias signaloutput of said summing junction being electrically connected to saidcomparing means and said temperature sensor and said humidity sensorbeing located adjacent the inlet to said compressor.
 8. The combinationof claim 4 wherein the means for sensing and generating apressure-response signal is a pressure transducer.
 9. The combination ofclaim 1 wherein said adjusting means is a flow bypass having poweredactuating means, said flow bypass being in flow communication with saidsteam generating means.
 10. The combination of claim 2 wherein saidadjusting means is a flow bypass having powered actuating means, saidflow bypass being in flow communication with the outlet of said turbine,with said steam generating means and with mixing means locateddownstream in the turbine exhaust system.
 11. In a gas turbine powerplant wherein the turbine is mechanically connected to and drives acompressor; said compressor supplies compressed air to a combustor inflow communication therewith; steam injecting means including steamgenerating means is in flow communication with said combustor andgenerates and supplies steam thereto; means in flow communication withsaid combustor supplies fuel thereto for combustion thereof with air insaid combustor for the generation of hot gases, and said combustorsupplies the hot gases generated therein to said turbine being in flowcommunication therewith, the combination with said steam generatingmeans of means to automatically control steam flow to said combustor,said control means comprising: a. means in flow communication with saidcompressor for generating a control signal and b. means for adjustingthe admission of steam to said combustor, said adjusting means being inflow communication with both said steam injecting means and saidcombustor and being automatically responsive to said control signal. 12.The combination of claim 11 wherein said steam generating means is inflow communication with the exhaust system of said turbine.
 13. Thecombination of claim 11 wherein the means for generating a controlsignal comprises: a. electrical signal comparing means having first andsecond inputs and having an output, said output being electricallyconnected to said adjusting means, b. means electrically connected tosaid first input of said comparing means and in flow communication withthe compressor discharge for sensing the compressor discharge pressureand generating a pressure-respOnse signal quantitatively related theretoand c. means electrically connected to said second input of saidcomparing means for applying a bias signal thereto, said comparing meanssupplying a control signal to said adjusting means via said output whenthe relationship between said bias signal and said pressure-responsesignal deviates from some pre-determined value.
 14. The combination ofclaim 13 wherein said means for applying a bias signal is a fixedvoltage source.
 15. The combination of claim 13 wherein said means forapplying a control bias signal includes a voltage generator and atemperature sensor having an electrical signal output quantitativelyrelated to the temperature sensed, said temperature sensor being locatedadjacent the inlet to said compressor and being electrically connectedto said voltage generator, said voltage generator being electricallyconnected to said second input and the bias signal generated therebybeing quantitatively related to the signal from said temperature sensor.16. The combination of claim 13 wherein the means for applying a biassignal includes a temperature sensor having an electrical signal outputquantitatively related to the temperature sensed; first and secondvoltage generators electrically connected at their respective inputs tosaid temperature sensor; a humidity sensor having an electrical signaloutput quantitatively related to the relative humidity sensed, a voltagemultiplier having separate inputs electrically connected to the outputsof said second voltage generator and said humidity sensor, respectively;and the outputs of said first voltage generator and said voltagemultiplier being electrically connected to a summing junction, theoutput of said summing junction being electrically connected to saidcomparing means and said temperature sensor and said humidity sensorbeing located adjacent the inlet to said compressor.
 17. The combinationof claim 13 wherein the means for sensing and generating apressure-response signal is a pressure transducer.
 18. The combinationof claim 11 wherein said adjusting means is a flow by-pass havingpowered actuating means.
 19. In a gas turbine power plant wherein aliquid-cooled turbine is mechanically connected to and drives acompressor; said compressor supplies compressed air to a combustor inflow communication therewith; steam injecting means including steamgenerating means is in flow communication with said combustor andsupplies steam thereto; means in flow communication with said combustorsupplies fuel thereto for combustion thereof with air in said combustorfor the generation of hot gases and said combustor supplies the hotgases generated therein to said turbine being in flow communicationtherewith, the combination with said steam injecting means of: a. firststeam generating means in flow communication with the exhaust system ofsaid turbine, b. second steam generating means in series with said firststeam generating means; said second steam generating means being in heatexchange relationship with the cooling circuit of said turbine, c. meansin flow communication with said compressor for generating a controlsignal and d. means connected to said control signal generating meansand responsive to said control signal for adjusting the flow of exhaustgas to said first steam generating means.
 20. The combination of claim19 wherein the means for generating a control signal comprises: a.electrical signal comparing means having first and second inputs andhaving an output, said output being electrically connected to saidadjusting means, b. means electrically connected to said first input ofsaid comparing means and in flow communication with the compressordischarge for sensing the compressor discharge pressure and generating apressure-response signal quantitatively related thereto and c. meanselectrically connected to said second input of said comparing means forapplying a bias signal thereto, said comparIng means supplying a controlsignal to said adjusting means via said output when the relationshipbetween said bias signal and said pressure-response signal deviates fromsome predetermined value.
 21. The combination of claim 20 wherein saidmeans for applying a bias signal is a fixed voltage source.
 22. Thecombination of claim 20 wherein said means for applying a bias signalincludes a voltage generator and a temperature sensor having anelectrical signal output quantitatively related to the temperaturesensed, said temperature sensor being located adjacent the inlet to saidcompressor and being electrically connected to said voltage generator,said voltage generator being electrically connected to said second inputand the bias signal generated thereby being quantitatively related tothe signal from said temperature sensor.
 23. The combination of claim 20wherein the means for applying a bias signal includes a temperaturesensor having an electrical signal output quantitatively related to thetemperature sensed; first and second voltage generators electricallyconnected at their respective inputs to said temperature sensor; ahumidity sensor having an electrical signal output quantitativelyrelated to the relative humidity sensed; a voltage multiplier havingseparate inputs electrically connected to the outputs of said secondvoltage generator and said humidity sensor, respectively; and theoutputs of said first voltage generator and said voltage multiplierbeing electrically connected to a summing junction, the bias signaloutput of said summing junction being electrically connected to saidcomparing means and said temperature sensor and said humidity sensorbeing located adjacent the inlet to said compressor.
 24. The combinationof claim 20 wherein the means for sensing and generating apressure-response signal is a pressure transducer.
 25. The combinationof claim 19 wherein said adjusting means is a flow bypass having poweredactuating means, said flow bypass being in flow communication with saidsteam generating means.
 26. The combination of claim 19 wherein saidadjusting means is a flow bypass having powered actuating means, saidflow bypass being in flow communication with the outlet of said turbine,with said steam generating means and with mixing means locateddownstream in the turbine exhaust system.
 27. In the operation of a gasturbine power plant in the steam injection mode wherein the followingsteps are performed: generating steam from liquid water; compressingatmospheric air to superatmospheric pressure; passing the compressed airto a combustion zone, where fuel is introduced and continuous combustionoccurs; passing the generated steam to said combustion zone, and passinghot gases continuously from said combustion zone through an expansionzone where mechanical energy is abstracted in substantially greateramount than the mechanical energy absorbed in the compression step, thecombination with said series of step of: a. automatically controllingthe flow of steam to said combustion zone by means of a control signal,said control signal resulting from the interrelation of a bias signaland a signal quantitatively comparable to the compressor pressure ratio.28. The steps of operation of a gas turbine power plant as recited inclaim 27 wherein the bias signal is a constant voltage signal.
 29. Thesteps of operation of a gas turbine power plant as recited in claim 27wherein the bias signal is quantitatively related to the ambienttemperature.
 30. The steps of operation of a gas turbine power plant asrecited in claim 27 wherein the bias signal is quantitatively relatedboth to the ambient temperature and to the ambient humidity.